Under the Köppen Climate Classification climate classification, "dry-summer subtropical" climates are often referred to as "Mediterranean". This climate zone has an an average temperature above 10°C (50°F) in their warmest months, and an average in the coldest between 18 to -3°C (64 to 27°F). Summers tend to be dry with less than one-third that of the wettest winter month, and with less than 30mm (1.18 in) of precipitation in a summer month. SMany of the regions with Mediterranean climates have relatively mild winters and very warm summers.

The Köppen Climate Classification subtype for this climate is "Csb". (Mediterran Climate).

The average amount of precipitation for the year in Asotin is 15.4" (391.2 mm). The month with the most precipitation on average is May with 2.3" (58.4 mm) of precipitation. The month with the least precipitation on average is February with an average of 0.8" (20.3 mm). There are an average of 73.0 days of precipitation, with the most precipitation occurring in May with 10.0 days and the least precipitation occurring in January with 4.0 days.

In Asotin, there's an average of 13.9" of snow (0 cm). The month with the most snow is January, with 4.2" of snow (10.7 cm).